[amie38478]

What causes the yellow leaves on my gardenia bushes. They r very healthly looking other wise

[amie38478]

When do I need to prune my plum trees

[KUXJ]

Hi!amie38478, and welcome to AMHD :)

what causes the yellow leaves on my gardenia bushes. they r very healthly looking other wise

You don't mention your locality, but here are three areas to look at:

The leaves yellowing could be due to salt build-up from excess watering with high salt content water.
If the soil is poorly drained and water-logged, the plant needs to be located in an area of higher elevation relative to the area where it now resides.
Using mulch to help keep the soil moist and add to the organic matter is a good gardening practice and allows you to water less often, which is particularly important if your water is high in salt content.

Leaf yellowing is sometimes a sign of nitrogen deficiencey, but be careful not to overfertilize, because this can damage the plant and always is a risk to the environment by run-off into groundwaters.
During the growing season you could lightly fertilize monthly with a balanced acid based plant fert or fish emulsion.

And last chlorosis.
Chlorosis - Focus on Plant Problems - University of Illinois Extension

Growing info:
http://hort.ifas.ufl.edu/shrubs/GARJASA.PDF

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As for your plum tree...
With most fruit trees you prune in the winter to reshape and in the summer to encourage fruit.
It is better not to prune in the winter as it takes longer for the wound to heal and then are susceptible to a disease called silver leaf.

If your locality is going into its Fall season...

And you still haven't had your first frost remove some of the new growth that is crowded or any that is growing straight up. Of the new growth that is left cut back about half of them to about three or four leaves. These will develop fruit buds.
The other branches can get a light pruning (just remove the tips on sturdy branches and a bit more on weaker branches) they will then support plums in future years without breaking. By doing this you should get a light crop next year followed by successive heavier ones.

How to Prune Plum Trees - wikiHow


K